Ethylenically unsaturated chlorinated hydrocarbons (hereinafter noted as EUCH) find many uses in commercial processes. Chlorinated ethylenes such as vinyl chloride, vinylidene chloride, trichloroethylene and perchloroethylene have diverse uses in industry. During preparation and use of the EUCH, gas streams containing small amounts of these materials are produced and usually vented to the atmosphere. The EUCH can contribute to the production of smog in the atmosphere and certain compounds are believed to be deleterious to the environment.
Gaseous emissions containing EUCH can arise in processes for the preparation of 1,2-dichloroethane, in processes in which chloroethyl phosphate or phosphonate compositions are dehydrohalogenated or condensed, in processes for preparation of vinyl chloride monomer, in processes in which vinyl chloride is polymerized to polyvinyl chloride, in processes for drying vinyl chloride containing polymers, during fabrication of articles from polyvinyl chloride, in copolymerization processes in which vinyl chloride or vinylidene chloride are monomers or comonomers in polymerization with non-chlorine containing monomers, and in vapor phase degreasing processes in which trichloroethylene or perchloroethylene are used as the solvents.
The vents from the reactors and ventilation air from the area around the reactors, mills and degreasers usually contain small amounts of the EUCH. Since these chlorinated materials are present in the gas stream in small concentrations, they are usually difficult to economically recover or remove from the gas stream.
It has been proposed to remove the chlorinated materials from gas streams by incinerating the gas streams to convert the chlorinated materials to hydrogen chloride, water and carbon dioxide. However, when the chlorinated materials are present in the gas stream in only small amounts, or contain a relatively large proportion of chlorine, the energy required to heat the gas stream to a temperature sufficiently high to destroy the compounds is large. The large energy requirement makes the process unattractive for application in many commercial applications.
It has also been proposed to adsorb chlorinated hydrocarbons from gas streams on activated carbon. This method is difficult to operate where large volumes of gas containing only small amounts of chlorinated hydrocarbons must be processed. The method requires that energy be provided to pump the gas stream through the relatively large pressure drop across a bed of activated carbon. In addition, the activated carbon must be regenerated if the method is to remain effective.
A solution to this problem has been sought for some time. Ideally such a solution would substantially reduce the amount of EUCH in a gas stream in a manner which is simple, can be operated inexpensively and safely and provide for a substantial reduction in the amount of EUCH in the gaseous stream.
It is an object of the present invention to provide a method for reducing the amounts of EUCH in gas streams. It is an object of the present invention to provide a simple, relatively inexpensive method for reducing the amount of vinyl chloride, dichloroethylene, trichloroethylene and perchloroethylene in gas streams. It is a further object of the present invention to provide a method for substantially reducing the amounts of vinyl chloride and vinylidene chloride in gas streams which arise from the production of these EUCH, the polymerization of these materials to polymers and the fabrication of the polymers into utilitarian articles.